Optimized Method for Mapping Inorganic Pigments by Means of Multispectral Imaging Combined with Hyperspectral Spectroscopy for the Study of Vincenzo Pasqualoni’s Wall Painting at the Basilica of S. Nicola in Carcere in Rome

Multispectral imaging is a preliminary screening technique for the study of paintings. Although it permits the identification of several mineral pigments by their spectral behavior, it is considered less performing concerning hyperspectral imaging, since a limited number of wavelengths are selected. In this work, we propose an optimized method to map the distribution of the mineral pigments used by Vincenzo Pasqualoni for his wall painting placed at the Basilica of S. Nicola in Carcere in Rome, combining UV/VIS/NIR reflectance spectroscopy and multispectral imaging. The first method (UV/VIS/NIR reflectance spectroscopy) allowed us to characterize pigment layers with a high spectral resolution; the second method (UV/VIS/NIR multispectral imaging) permitted the evaluation of the pigment distribution by utilizing a restricted number of wavelengths. Combining the results obtained from both devices was possible to obtain a distribution map of a pictorial layer with a high accuracy level of pigment recognition. The method involved the joint use of point-by-point hyperspectral spectroscopy and Principal Component Analysis (PCA) to identify the pigments in the color palette and evaluate the possibility to discriminate all the pigments recognized, using a minor number of wavelengths acquired through the multispectral imaging system. Finally, the distribution and the spectral difference of the different pigments recognized in the multispectral images, (in this case: red ochre, yellow ochre, orpiment, cobalt blue-based pigments, ultramarine and chrome green) were shown through PCA false-color images

Characterization of elemental and firing-dependent properties of Phlegrean ceramics by non-destructive ED-XRF and NMR techniques

A combination of energy dispersive X-ray fluorescence (ED-XRF) and 2D proton nuclear magnetic resonance (1H NMR) relaxometry was employed for the characterization of two groups of similar ceramic fragments from the high-medieval production of the Phlegrean area (Miseno and Cuma, Southern Italy). Both methods are based on the use of non-destructive and portable instruments. This approach allows to correlate complementary microstructural features of ceramics, both dependent and independent of the firing technique.The ED-XRF analysis has shown up the degree of elemental homogeneity of these two ceramic populations and has lead to reasonable hypotheses about continuity in raw clay source utilization and manufacturing methods over the time period of this Phlegrean ceramic production (VI-XIII centuries A.D.), which have proven coherent with literature data.The NMR investigation has allowed to reveal the structural differences among findings, concerning pore space topology and the magnetic attributes of pore walls. Such differences have been associated to the peculiar interplay between temperature and duration of firing and have proven in step with the temperature assignments provided by archaeologists.This way the usefulness of the proposed methodology for the characterization of the microstructural fingerprint of ancient ceramics has been clearly shown and reliable conclusions about the technological evolution of and the mutual influence between the investigated ceramic productions have been drawn

Study on the technique of the Roman age mural paintings by micro-XRF with Polycapillary Conic Collimator and micro-Raman analyses

XRF and micro-Raman stratigraphic microanalyses of fragments of some mural paintings, belonging to the Archaeological Site of Oplonti (Napoli) and the Vigna Barberini site in the Palatino (Roma), were performed. In order to collimate the fluorescence X-rays emitted by the samples, an X-ray polycapillary conic collimator (PCC) has been used in front of the detector. This device arrangement is compact, versatile, and portable. The nature of the pigments, the compositional elements, and the thickness of the fragment layers have been studied. The stratigraphic analysis partially confirms the preparation techniques described by Plinius and Vitruvius; moreover it confirms the hypothesis that the artifacts are not fresco paintings. This work has been conducted within the context of a wider research on the Roman age mural paintings. (c) 2005 Elsevier SAS. All rights reserved

Charlemagne's Black Marble: the Origin of the Epitaph of Pope Hadrian I

Charlemagne's Black Marble: the Origin of the Epitaph of Pope Hadrian